1. Field of the Invention
The present invention relates to vehicular radar systems, and more particularly, to a method and apparatus for improved vehicular collision avoidance by tracking the relative movement of an object and providing an operator of a vehicle an indication of the object's proximity to the vehicle.
2. Description of the Prior Art
Studies have shown that there is an ever-increasing number of vehicles traveling the nation's roadways. Correspondingly, these studies have shown that there is an increase in the likelihood of vehicular collisions with moving as well as stationary objects. For a number of years, automobiles have been sold with safety devices designed to help the occupants of a vehicle survive a collision. These safety items include high impact bumpers, high traction tires, seat-belts, air-bags, crumple-zones and side-impact protection systems. In addition to these safety items, additional features that assist in avoiding a collision such as anti-lock brakes are now commonly available. Safety devices have become an important selling point for automobile manufacturers and an important consideration for consumers. As important as these safety features have become, a reliable collision warning system that would substantially obviate the need for collision survival devices is yet to be developed.
Recent studies released by Mercedes-Benz have determined that at least sixty (60) percent of rear-end collisions, thirty (30) percent of head-on collisions and fifty (50) percent of intersection accidents could be avoided if the operator of the vehicle was provided at least one-half (0.5) second more "lead-time" before impact. In order to provide the additional lead-time, collision warning radar systems have been developed for incorporation in motor vehicles. The typical collision warning system operates by measuring the relative position, speed and direction of targets proximate the vehicle. The current systems are relatively unreliable and are often activated prematurely or at a time when the collision can not be avoided (i.e., just before impact). In addition, current collision warning systems are not commercially available because they are incapable of simultaneously reliably tracking numerous closely located objects (i.e., cars, highway dividers, trees, barriers, etc.) and of reliably determining if an object is becoming a greater or lesser danger.
Current state-of-the-art collision warning systems, such as that disclosed in U.S. Pat. No. 5,302,956, use scanning and digital signal processing (DSP) techniques to monitor the relative speed and range of a target based upon the frequency and phase difference of two distinct signals. Information relating to each target in the system's field of view is provided to a microcontroller which typically includes an audio warning unit. The microcontroller processes the frequency and phase information to determine if a condition exists that requires action on the part of the operator (i.e., if a target is close to the operator's vehicle). If a threatening condition exists, the audio warning unit is activated to alert the vehicle's operator. The extent of the audible warning is usually proportional to the degree of danger (i.e., the speed and proximity of the target to the vehicle).
A major disadvantage of the state of the art collision warning systems is that target drop outs due to maneuvering of a target out of the vehicle's field of view, measurement errors and signal noise are not taken into account. Specifically, the prior art systems do not monitor trends of each target's relative speed and range to match new speed and range readings. As a result, if a target being monitored moves out of the field of view of the radar or if mismeasurement occurs for even a small period of time, the previously stored data that is not associated with any new target data will be deleted. If the same target then reappears in the field of view, the new target data will not be associated with any previously recorded data because the new target data is substantially different from the previously stored data. Therefore, the system is not able to provide the operator with an indication of whether each target is becoming a greater or lesser threat to the vehicle. As a result, the current system will identify the new data as a new target not previously encountered.
The prior art collision warning systems are also deficient in that if a measurement error occurs when the target is in the vehicle's warning zone, the system will not provide the vehicle's operator with the necessary warning in order to avoid a collision. Furthermore, the prior art collision warning systems have limited use as accident reconstruction systems since they have only limited data storage capability. As a result, if the vehicle is involved in an accident and the operator does not remember to shut-off the data recording instrumentation, the relevant data for "off-line" accident reconstruction will be lost. Finally, the traditional collision warning systems do not have the capability to predict the future movements of each target and thus better anticipate when a dangerous condition might arise. Other deficiencies of the traditional collision warning systems are apparent to those skilled in the art.